1. Field of the Invention
The present invention relates in general to a recording-medium supply device arranged to feed recording media such as cut sheets one after another from a stack of the recording media, and an image-recording apparatus such as a printer, a copier and a facsimile device including a recording device and the recording-medium supply device to feed the cut sheets to the recording device. The invention is also concerned with an image-recording apparatus wherein the recording-medium supply device has a plurality of medium supply cassettes each of which is arranged to feed the recording media from a stack of the recording media to the recording device of the apparatus.
2. Discussion of Related Art
One type of known image-recording apparatus such as a printer, a copier and a telecopier (facsimile device) uses an ink-jet recording head as a recording device operable to record an image in a matrix of dots, on a recording medium such as a paper sheet while the recording medium is fed. The ink-jet recording head may suffer from a failure to normally eject droplets of ink, due to air bubbles staying within the recording head during its recording operation. To recover the ink-jet recording head from the ink ejection failure, the image-recording apparatus has a maintenance device outside a recording area in which the recording operation by the recording head on the recording medium is possible. This maintenance device includes a purging pump, and a sucking portion which is connected to the purging pump and an ink ejection part (nozzles) or an air-bubble chamber of the recording head and which is periodically operated to remove a volume of the ink that contains the air bubbles.
JP-8-174958A discloses an example of a solution to solve the drawback described above. According to this solution, the recording apparatus is provided with a kicker member actuated by a movement of the recording head in a main scanning direction perpendicular to a secondary scanning direction which is a direction of feeding of the recording medium. The kicker member is arranged to shift an idler gear which selectively meshes with a first gear train for transmitting a drive force from a drive motor to a medium feeding roller platen) to feed the recording medium, or a second gear train for transmitting the drive force to the maintenance device to drive the purging pump, so that the idler gear is shifted into meshing engagement with the second gear train by the kicker member by a movement of the recording head upon operation of the maintenance device.
For easier assembling of the first gear train, second gear train and idler gear, the gears have some amount of clearance with respect to support shafts. Further, the gears inevitably have a backlash between the surfaces of the meshing teeth, due to limited accuracy of shaping of the gear teeth. In view of these clearance and backlash, the drive motor selectively used to feed the recording medium and drive the purging pump is controlled upon a shifting action of the idler gear to selectively mesh with the first or second gear train, such that the drive motor is first rotated in a forward direction by an angle corresponding to a half of a width angle of a tooth of the gears in question, and is then rotated in a reverse direction by an angle corresponding to a multiple of the width angle, for facilitating disengagement of the idler gear from one of the first and second gear trains and engagement of the idler gear with the other gear train.
A recently developed image-recording apparatus is provided with a plurality of medium supply cassettes that accommodate respective stacks of recording media such as paper sheets of different sizes, so that the recording operation is performed on the recording medium of the selected size. The medium supply cassettes are arranged in a stack in the vertical direction below a carriage drive device. According to a signal indicative of the selected size of the recording medium, a medium supply roller is brought into contact with the uppermost one of the recording media of the stack accommodated in a selected one of the medium supply cassettes which corresponds to the selected size, and the uppermost recording media (uppermost paper sheet) is fed by the medium supply roller along a U-turn path extending from one end of the selected medium supply cassette, to the recording portion disposed below the carriage drive device.
Where the image-recording apparatus is provided with a plurality of medium supply cassettes (e.g., two cassettes), however, the above-described power-transmission switching device arranged to shift the idler gear for selective meshing engagement with the first and second gear trains has a drawback. Namely, the power-transmission switching device as applied to the image-recording apparatus provided with two medium supply cassettes, for example, may include a large-diameter idler gear disposed between the first gear train to drive the medium supply roller or the upper medium supply cassette and the second, gear train to drive the purging pump. The first gear train includes a small-diameter gear located on one side of the large-diameter idler gear, while the second gear train includes a small-diameter gear located on the other side of the large-diameter idler gear, and the large-diameter idler gear is kept connected to the drive motor. However, this type of power-transmission switching device does not permit the drive force to be transmitted to a gear train to drive the medium supply roller for the lower medium supply cassette. Therefore, another idler gear is necessary to selectively drive the medium supply rollers for the two medium supply cassettes, and the arrangement to selectively transmit the drive force from the same drive motor to the medium supply rollers for the two medium supply cassettes and the maintenance portion tends to be complicated in construction.
For simplifying control systems for an image-recording apparatus provided with a single medium supply cassette and an image-recording apparatus provided with a plurality of medium supply cassettes (e.g., two cassettes), it is desirable that the above-described control to rotate the drive motor in the forward and reverse directions as disclosed in JP-8-174958A is applicable to those two types of image-recording apparatus.
JP-2002-249248A discloses an example of a recording-medium supply device wherein a medium supply roller for ceding cut sheets stacked in a medium supply cassette is supported by a free end portion of a roller support arm that is pivotally attached to a support shaft which is disposed above the medium supply cassette so as to extend in a direction perpendicular to the feeding direction of the cut sheets. The roller arm is pivotally biased by a spring such that the medium supply roller is held in contact with the uppermost cut sheet of the stack, irrespective of the number of the cut sheets stacked in the medium supply cassette, namely, the height of the stack of the cut sheets.
In the recording-medium supply device constructed as described above, the position of abutting contact of the medium supply roller with the uppermost cut sheet varies in not only the direction of height of the stack of the cut sheets (direction of stacking of the cut sheets) but also the feeding direction of the cut sheets, with a change of the height of the stack, since the roller support arm supporting the medium supply roller at its free end portion is pivotally supported. A large amount of variation in the position of abutting contact of the medium supply roller with the uppermost cut sheet in the feeding direction with a change of the height of the stack undesirably deteriorates the stability of feeding of the cut sheets from the medium supply cassette.
The roller support arm which is attached at its proximal end portion to the support shaft pivotally about the support shaft has some amount of play at its proximal or fixed end portion in the axial direction of the support shaft, which causes a rattling movement of the roller support arm at its proximal end portion in the direction perpendicular to the longitudinal direction of the roller support arm, namely, in the axial direction of the support shaft. This axial rattling movement of the roller support arm at the proximal end portion causes a rattling movement at the free end portion, which is generally larger than that at proximal end portion, due to a clearance between the outer circumferential surface of the support shaft and the inner circumferential surfaces of shaft holes through which the support shaft extends.
Where the medium supply cassette has a relatively large storage capacity, the roller support arm has an accordingly large length, so that the rattling movement at the proximal end portion of the support arm is greatly amplified into the rattling movement at the free end portion, whereby the axis of rotation of the medium supply roller is inclined with respect to the direction perpendicular to the feeding direction. This inclination prevents the medium supply roller from feeding the cut sheets exactly in the feeding direction, giving rise to a risk of jamming of the fed cut sheets in the feeding path.
In the recording-medium supply device disclosed in JP-2002-249248A, auxiliary rollers are provided between a lower medium supply cassette and the recording portion of the image-recording apparatus. Without such auxiliary rollers, an actual path of feeding of the cut sheet fed by the medium supply roller obliquely with respect to the nominal direction of feeding from the cassette greatly deviates from the nominal feeding path between the cassette and registering rollers, resulting in easy jamming of the cut sheet in the feeding path. Where the obliquely fed cut sheet reaches the registering rollers, the cut sheet which is registered by the registering rollers for parallelism of the longitudinal direction of the registered cut sheet with the nominal feeding direction tends to be undesirably shifted in the widthwise direction of the cut sheet, so that an image printed by the recording portion on the registered cut sheet is not correctly centered in the widthwise direction (perpendicular to the feeding direction).